The present invention relates to a system and method for sorting mass recyclables and more particularly to a system for sensing and sorting white paper from other objects.
It will be appreciated by those skilled in the art that society desires to recycle as much of its waste materials as possible. For example, aluminum cans, plastic bottles, and other items have been the source of mixed recyclable efforts in the past. The assignee of the present application, Magnetic Separation Systems, Inc. (MSS) is a world leader in mixed recyclables. MSS is also the owner of many patents disclosing technologies for sorting and concentrating aluminum and sorting plastics.
One other type of mixed recyclable is paper. In the past, recyclable efforts have been dominated by hand sorting of paper by type. One common effort is curbside recycling. Other efforts have been to sort paper from other types of materials. Unfortunately, as with any other procedure, any type of hand sorting requires an intensive use of labor that is not always efficient.
What is needed, then, is a method and system that can sort white paper from a stream of other paper. This needed system must also be capable of sorting a stream of material from white paper in case the stream is dominated by materials other than white paper. The system must decrease the amount of labor presently being used. The system must be economical. The system must be effective. The system is presently lacking in prior art.
The present invention discloses a system and method for sorting white paper, and especially a type of white paper commonly referred to as bright white paper, from other objects. One reason that recycling of bright white paper is very desirable is that the fluorescent chemicals added to such papers are expensive plus the bright white paper tends to be a very high quality paper fiber. Thus, this is a premium paper fraction for recycling. The system may also sort other objects from white paper.
The present invention uses an energy source that is preferably an ultraviolet light light that is concentrated in some manner onto an object. The energy is focused on the paper. If the paper is bright white paper, the ultraviolet radiation will cause the brightening agents in the white paper to fluorescence into an energy having a different and longer wavelength. The fluorescence is then measured.
The system and method of the present invention is particularly adapted for use in sensing the presence of bright white paper that flows past the sensor on a conveyor. The conveyor is constantly illuminated with the ultraviolet light. Also, a second light source is provided which periodically illuminates an inspection zone of the conveyor with a second light which is in the visible light spectrum, and preferably in the blue-green portion of the visible light spectrum.
A sensor located above the inspection zone of the conveyor collects light from the inspection zone of the conveyor. The collected light includes both emitted fluorescence from bright white paper located in the inspection zone and reflected light from the second light source reflected off of objects in the inspection zone.
Periodically, the sensing system senses first and second parameters of the light collected from the inspection zone. The first parameter is the level of reflection of the second light source in order to determine whether any object is present on the conveyor in the inspection zone. The second parameter sensed is the level of fluorescent light to determine whether an object present in the inspection zone is bright white paper.
Thus, if the sensed level of the reflected light from the second light source is below a certain threshold, the system will determine that no object is present in the inspection zone on the conveyor. If the sensed level of reflected light from the second light source is above a threshold level, the system will sense that some object is present in the inspection zone on the conveyor, but the identification of that object will depend upon the sensed level of fluorescent energy coming from that object. If the sensed level of fluorescent energy from the object is below a threshold level, the system will determine that the object is something other than bright white paper. If the sensed level of fluorescent energy is above a predetermined threshold, the system will determine that the sensed object is bright white paper.
The system may then send control signals to an ejection means which will eject either the bright white paper fraction or the non-bright white paper fraction from the paper stream flowing across the conveyor.
Accordingly one object of the present invention is to provide a system and method for sensing and sorting bright white paper from other objects.
Another object of the present invention is to provide a system that allows someone to sort bright white paper from other objects that is not labor intensive.
Another object of the present invention is to provide a system that can sort both bright white paper from other objects and other objects from bright white paper.
Still a further object of the present invention is to provide an accurate system for sensing bright white paper.
Other and further objects features and advantages of the present invention will be readily apparent to those skilled in the art upon a reading of the following disclosure when taken in conjunction with the accompanying drawings.